Pressure and pressure‐gradient sensitivity of the tadpole medulla

The dorsal medulla of anuran tadpoles undergoes significant anatomical reorganization over metamorphic development. To examine how functional properties alter in response to anatomical changes, we recorded single and multiple unit activity in the medulla of bullfrog tadpoles to a sinusoidal‐oscillating dipole source that traversed the length of the animal’s body. This dipole stimulus has been used previously to distinguish between pressure‐sensitive auditory responses in the saccular nerve of the goldfish and pressure‐gradient lateral line responses in the lateral line nerves of goldfish and other teleost fish. Recording sites in the developing dorsal lateral nucleus showed pressure‐type responses to dipole stimulation near the animal’s head and lung. Evidence for the role of the bronchial columella and the air‐filled lungs acting as a sound pressure transducer in mediating these responses was equivocal. Recording sites in the lateral line nucleus and surrounding neuropil showed pressure‐gradient‐type res...